Tumor cells from a UV-induced C3H fibrosarcoma express a multiplicity of unique tumor-specific antigens. These products, defined by cloned T-cell lines, appear to play an important role in the immune response of the host to the tumor. Using monoclonal antibodies with unique specificity for this tumor, several of these antigens have recently been characterized as bona fide transplantation antigens alien to the C3H mouse. Therefore, we plan to clone and characterize the genes encoding these novel transplantation antigens to establish the genetic basis for their anomalous expression, i.e., their multiplicity and uniqueness. The molecular cloning of these genes should provide unique opportunities to study the relationship between the class I diversification and the immunopathology of this neoplastic disease. This research work is submitted as a companion to that of Dr. Hans Schreiber on the immunobiology of these tumor-specific unique MHC antigens. (AG)